Communication system

ABSTRACT

A communication system is disclosed in which a base station receives, from a core network entity, a paging request for paging an MTC device. The base station determines a paging occasion for sending to said MTC device paging related information, wherein the paging occasion is defined such that it identifies a plurality of subframes in which the paging related information can be sent and repeated. The base station sends (and repeats, as appropriate) the paging related information in the plurality of subframes identified by the paging occasion.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a National Stage of International Application No.PCT/JP2016/001951 filed Apr. 8, 2016, claiming priority based on BritishPatent Application No. 1506156.7 filed Apr. 10, 2015, the contents ofall of which are incorporated herein by reference in their entirety.

TECHNICAL FIELD

The present invention relates to mobile communications devices andnetworks, particularly but not exclusively those operating according tothe 3^(rd) Generation Partnership Project (3GPP) standards orequivalents or derivatives thereof. The invention has particularalthough not exclusive relevance to the Long Term Evolution (LTE) ofUTRAN (called Evolved Universal Terrestrial Radio Access Network(E-UTRAN)), including LTE-Advanced.

BACKGROUND ART

In a mobile (cellular) communications network, (user) communicationdevices (also known as user equipment (UE), for example mobiletelephones) communicate with remote servers or with other communicationdevices via base stations. In their communication with each other,communication devices and base stations use licensed radio frequencies,which are typically divided into frequency bands and/or time blocks.

In order to be able to communicate via the base stations, communicationdevices need to monitor control channels operated by the base stations.One of these control channels, the so-called physical downlink controlchannel (PDCCH) and/or the so-called evolved PDCCH (EPDCCH) in Rel-13,carries the scheduling assignments and other control information. The(E)PDCCH serves a variety of purposes. Primarily, it is used to conveythe scheduling decisions to individual communication devices, i.e.scheduling assignments for uplink and downlink communication.

The information carried on the (E)PDCCH is referred to as downlinkcontrol information (DCI). Physical control channels, such as the(E)PDCCH, are transmitted on an aggregation of one or severalconsecutive control channel elements (CCEs), where a control channelelement corresponds to nine resource element groups (REGs). Each REG hasfour resource elements (REs).

A paging channel is provided over (mapped to) the physical downlinkshared channel (PDSCH) for notifying communication devices about asystem information change and/or incoming communications for one or morecommunication devices (such as mobile terminated calls, short textmessages, downlink data, and/or the like). Paging messages (althoughthey are transmitted over the PDSCH) are scheduled via the (E)PDCCH.Specifically, in each radio frame transmitted by the base station thereis at least one predetermined paging occasion (PO) (a maximum of fourPOs per radio frame), each PO being a subframe in which the base stationmay transmit control data over the PDCCH in order to schedule anassociated paging message. Each paging message can identify one or morecommunication devices for which the paging message is sent. Whenever aPO includes a so-called paging identifier, i.e. a paging radio networktemporary identifier (P-RNTI), which is the same for all LTE devices inthe cell, each communication device processes the control data, andproceeds to decoding the paging message broadcast over the pagingchannel (at the time-frequency resource identified by the control data).

In more detail, whenever there is downlink data (or incoming call) for aparticular communication device, the network notifies the basestation(s) that may be serving that communication device about the data(or call). In response to this, the base station generates a radioresource control (RRC) paging message and transmits the generated pagingmessage for the communication device (by broadcasting via the PDSCH).The paging message is scheduled using one of the predetermined POs, thelocation of which is known to the communication devices (e.g. from thebase station's system information broadcast). The paging messageincludes one or more paging records identifying each communicationdevice being paged and the reason for paging that communication device.

If a communication device finds the (E)PDCCH addressed by P-RNTI in (thecontrol data sent via) the PO, then it proceeds to receiving anddecoding the RRC paging message from the PDSCH resource block (RB)identified by the associated control data transmitted via the PDCCH PO.If a paging record is found for a particular communication device in thedecoded RRC paging message, then that communication device proceeds torespond to the paging message (whilst other, non-paged, communicationdevices continue monitoring for the next PO). If appropriate, the pagedcommunication device performs a random access procedure with the basestation in order to establish a connection with the network and to beable to respond to the incoming communication that the paging message(i.e. the communication device's paging record) relates to.

Recent developments in telecommunications have seen a large increase inthe use of machine-type communications (MTC) devices which are networkeddevices arranged to communicate and perform actions without humanassistance. Examples of such devices include smart meters, which can beconfigured to perform measurements and relay these measurements to otherdevices via a telecommunication network. Machine-type communicationdevices are also known as machine-to-machine (M2M) communicationdevices.

MTC devices connect to the network (after performing an appropriaterandom access procedure, if necessary) whenever they have data to sendto or receive from a remote ‘machine’ (e.g. a server) or user. MTCdevices use communication protocols and standards that are optimised formobile telephones or similar user equipment. However, MTC devices, oncedeployed, typically operate without requiring human supervision orinteraction, and follow software instructions stored in an internalmemory. MTC devices might also remain stationary and/or inactive for along period of time. The specific network requirements to support MTCdevices have been dealt with in the 3GPP technical specification (TS)22.368 V13.1.0 the contents of which are incorporated herein byreference.

For the Release 13 (Rel-13) version of the standards relating to MTCdevices, support for a reduced bandwidth of 1.4 MHz in downlink anduplink is envisaged. Thus, some MTC devices will support only a limitedbandwidth (typically 1.4 MHz) compared to the total LTE bandwidth and/orthey may have fewer/simplified components. This allows such ‘reducedbandwidth’ MTC devices to be made more economically compared to MTCdevices supporting a larger bandwidth and/or having more complicatedcomponents. Beneficially, the EPDCCH is transmitted over a relativelynarrow frequency spectrum (1.4 Mhz) that makes it compatible with Rel-13reduced bandwidth MTC devices.

The lack of network coverage (e.g. when deployed indoors), incombination with the often limited functionality of MTC devices, canresult in such MTC devices having a low data rate and therefore there isa risk of some messages or channels, such as the EPDCCH, not beingreceived by an MTC device. In order to mitigate this risk, it has beenproposed to increase the coverage of transmissions to support such MTCdevices (e.g. corresponding to 20 dB for frequency division duplex (FDD)transmissions).

One approach proposed for the enhancement of coverage, for so-called‘coverage enhanced MTC devices’, is the repetition of the sameinformation (e.g. a DCI sent over the EPDCCH) across multiple subframes(e.g. two, three, or four subframes). In other words, for coverageenhanced (CE) MTC devices, the base station duplicates the transmittedinformation in the time domain (the base station re-transmits the sameinformation in one or more subframes subsequent to the subframe in whichthat information is first sent). Such a coverage enhanced MTC device canbe configured to combine the multiple copies of the (same) informationreceived in the multiple subframes, and after combining the receivedinformation, the coverage enhanced MTC device is more likely to be ableto decode the received information successfully than based on a singlecopy of the transmitted information. Similarly to the repetition of thesame information by the base station, coverage enhanced MTC devices arealso configured to duplicate (in the time domain) informationtransmitted to the base station to facilitate successful reception ofthat information at the base station.

In practice, MTC devices may be deployed in different locations and theymay experience different channel conditions. Therefore, the number ofrepetitions may need to be tailored for each device's situation orcoverage level, and each MTC device informs its serving base station ofthe amount of coverage required (e.g. 5 dB/10 dB/15 dB/20 dB coverageenhancement) to allow the base station to adjust its control signallingappropriately.

Paging messages are transmitted separately for MTC devices (e.g.low-complexity and/or coverage enhanced MTC devices) and for other(non-MTC) communication devices, such as conventional mobile telephones.Furthermore, 3GPP envisaged that paging messages for MTC devices may betransmitted in different subbands in dependence on the MTC device's modeof operation (e.g. whether it is operating in normal coverage mode (0 dBCE level), at 5 dB CE level, at 10 dB CE level, or at 15 dB CE level).

SUMMARY OF INVENTION Technical Problem

It can be seen, therefore, that where the paging is intended for a CEMTC device repetition of transmissions will need to be supported.However, current paging procedures do not support such repetition.

Moreover, even if repetition were supported, there can be uncertainty,at the base station, regarding the type of MTC device being paged and/orits required coverage enhancement level which can result in an incorrectnumber of repetitions being used and/or paging messages being sent inthe wrong time-frequency resource, and/or with wrong format. Forexample, if the CE level is linked to the specific 1.4 MHz sub-band (thepaging location) in which paging communications are broadcast (ascurrently proposed by some 3GPP participants), then this uncertaintyregarding the CE level can result in some low-complexity MTC devicesbeing tuned to a 1.4 MHz bandwidth that is outside the subband overwhich the paging message (and/or the associated control data) istransmitted for these MTC devices. However, there is no trivial way ofensuring that the CE level employed by the communication device is thesame as the CE level employed by the base station (for thatcommunication device).

Accordingly, the present invention seeks to provide systems, devices andmethods which at least partially address the above issues.

Solution to Problem

In one aspect, the invention provides a base station for a communicationsystem in which machine type communication ‘MTC’ devices communicate viasaid base station, the base station comprising: means for determiningthat there is a requirement to notify said MTC devices that there hasbeen a system information update; means for notifying any idle mode MTCdevices about the system information update by sending a notificationusing a paging message; and means for providing any radio resourcecontrol ‘RRC’ connected mode MTC devices with the system informationusing MTC device dedicated signalling.

In one aspect, the invention provides a machine type communication ‘MTC’device for communicating with a base station, the MTC device comprising:means for forming a radio resource control ‘RRC’ connection with saidbase station to enter an RRC connected mode; a transceiver configured toobtain, using dedicated signalling, system information associated with acell of the base station, when in said RRC connected mode.

In one aspect, the invention provides a method performed by a basestation for a communication system in which machine type communication‘MTC’ devices communicate via said base station, the method comprising:determining that there is a requirement to notify said MTC devices thatthere has been a system information update; notifying any idle mode MTCdevices about the system information update by sending a notificationusing a paging message; and providing any radio resource control ‘RRC’connected mode MTC devices with the system information using MTC devicededicated signalling.

In one aspect, the invention provides a method performed by a machinetype communication ‘MTC’ device in a communication system in which MTCdevices communicate via a base station, the method comprising: forming aradio resource control ‘RRC’ connection with said base station to enteran RRC connected mode; and obtaining, using dedicated signalling, systeminformation associated with a cell of the base station, when in said RRCconnected mode.

Aspects of the invention extend to corresponding systems, methods, andcomputer program products such as computer readable storage media havinginstructions stored thereon which are operable to program a programmableprocessor to carry out a method as described in the aspects andpossibilities set out above or recited in the claims and/or to program asuitably adapted computer to provide the apparatus recited in any of theclaims.

Each feature disclosed in this specification (which term includes theclaims) and/or shown in the drawings may be incorporated in theinvention independently (or in combination with) any other disclosedand/or illustrated features. In particular but without limitation thefeatures of any of the claims dependent from a particular independentclaim may be introduced into that independent claim in any combinationor individually.

Embodiments of the invention will now be described by way of exampleonly with reference to the attached figures in which:

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 schematically illustrates a telecommunication system to whichembodiments of the invention may be applied;

FIG. 2 is a block diagram illustrating the main components of thecommunication device shown in FIG. 1;

FIG. 3 is a block diagram illustrating the main components of the basestation shown in FIG. 1;

FIG. 4 illustrates an exemplary way in which paging can be realised inthe system shown in FIG. 1;

FIG. 5 illustrates an exemplary paving configuration option that can beemployed in the system shown in FIG. 1;

FIG. 6 illustrates another exemplary paging configuration option thatcan be employed in the system shown in FIG. 1;

FIG. 7 illustrates another exemplary paging configuration option thatcan be employed in the system shown in FIG. 1;

FIG. 8 illustrates another exemplary paging configuration option thatcan be employed in the system shown in FIG. 1;

FIG. 9 illustrates an exemplary way in which a required coverageenhancement level (to be employed in a particular cell) can bedetermined for a communication device in the system shown in FIG. 1; and

FIG. 10 illustrates another exemplary way in which a required coverageenhancement level (to be employed in a particular cell) can bedetermined for a communication device in the system shown in FIG. 1.

DESCRIPTION OF EMBODIMENTS

<Overview>

FIG. 1 schematically illustrates a mobile (cellular) telecommunicationsystem 1 in which communication devices 3 (such as mobile telephone 3-1and MTC device 3-2) can communicate with each other and/or with othercommunication nodes via an E-UTRAN base station 5 (denoted ‘eNB’) and acore network 7. As those skilled in the art will appreciate, whilst onemobile telephone 3-1, one MTC device 3-2, and one base station 5 areshown in FIG. 1 for illustration purposes, the system, when implemented,will typically include other base stations and communication devices.

Each communication device 3 may fall into one or more categories of UEs.A first category of UEs include communication devices that support onlyan earlier release of the LTE standard (e.g. Rel-8, Rel-9, Rel-10,Rel-11, and/or Rel-12). Such communication devices are commonly referredto as legacy UEs (assuming that the base station 5 is operating inaccordance with Rel-13 of the LTE standards). It will be appreciatedthat some communication devices that belong to this category may notsupport the EPDCCH (only PDCCH). A second category of UEs includecommunication devices that support the current release of the LTEstandard (e.g. Rel-13 and/or later). A third category of UEs includereduced bandwidth UEs Rel-13 MTC devices capable of using a 1.4 Mhzbandwidth only), which are not able to communicate over the entirebandwidth available in the cell of the base station 5. A fourth categoryof UEs includes coverage enhanced UEs (e.g. some MTC devices), whichrequire certain base station functionalities to be simplified and/orrelaxed (although such coverage enhanced UEs may support otherfunctionalities as normal).

In this example, the mobile telephone 3-1 comprises a Rel-13 UE, and theMTC device 3-2 comprises a reduced bandwidth MTC device (which may alsobe configured for an appropriate level of coverage enhancement).Although not shown in FIG. 1, it is assumed that a number of other MTCdevices are also present within the cell of the base station 5.

The base station 5 is connected to the core network 7 via an S1interface. The core network 7 includes, amongst others: a gateway forconnecting to other networks, such as the Internet and/or to servershosted outside the core network 7; a mobility management entity (MME)for keeping track of the locations of the communication devices 3 (e.g.the mobile telephone and the MTC device) within the communicationnetwork 1; and a home subscriber server (HSS) for storing subscriptionrelated information (e.g. information identifying which communicationdevice 3 is configured as a machine-type communication device) and forstoring control parameters specific for each communication device 3.

The base station 5 is configured to transmit a physical downlink controlchannel (PDCCH) and an evolved PDCCH (EPDCCH) for reception by thecommunication devices 3 located within the base station's 5 cell. The(E)PDCCH allocates uplink and downlink resources to the communicationdevices 3. One difference between the PDCCH and the EPDCCH is that theEPDCCH uses a relatively narrow frequency spectrum (1.4 Mhz) that makesit compatible with Rel-13 reduced bandwidth MTC devices, whilst PDCCHuses a wider frequency spectrum in order to provide backwardcompatibility with legacy communication devices.

The so-called common search space (CSS) is a search space forall/multiple UEs in a cell to blindly decode the PDCCH(s) carryingdownlink control information (DCI) which is common to all/multiplecommunication devices 3. For example, the CSS may carry downlink controlinformation (DCI) for: system information blocks (SIBs) which containinformation related to cell access parameters; random access channel(RACH) messages; and/or the paging channel (PCH). In LTE Rel-13, the CSS(also referred to as ‘eCSS’) forms part of the search space of theEPDCCH.

Due to the reduced bandwidth of 1.4 MHz in downlink and uplink, the MTCdevice 3-2 cannot receive the PDCCH which is densely spread across theentire cell bandwidth (i.e. it may be transmitted over frequenciesfalling outside the 1.4 MHz supported by the MTC device 3-2). However,the MTC device 3-2 can receive the EPDCCH CSS (eCSS) which istransmitted over 6 RBs, i.e. within the 1.4 MHz hand supported by theMTC device 3-2.

In order to support MTC devices, the base station's 5 cell bandwidthincludes a number of subbands (e.g. non-overlapping subbands), eachsubband comprising 6 RBs (or less). Beneficially, since bandwidthreduced MTC devices are able to communicate over a maximum of 1.4 MHzbandwidth (which roughly corresponds to 6 RBs), the communication device3-2 is able to send and receive (eCSS and other) data over theparticular subband that its transceiver is currently tuned to.

Paging messages are transmitted separately for MTC devices (e.g.low-complexity and/or coverage enhanced MTC devices) and for othercommunication devices. Paging messages for MTC devices support PDSCHsubframe bundling/repetition with multiple bundle sizes/repetitionlevels accordance with the required level of coverage enhancement).Beneficially, the base station 5 paging the communication device 3-2 isprovided with information that allows it to determine that thecommunication device 3-2 comprises a low-complexity (bandwidth reduced)MTC device and/or an MTC device configured for coverage enhancement. Thebase station 5 is provided with information that allows it to determinethe amount of coverage enhancement (repetitions) required during pagingmessage transmission.

Advantageously, the base station 5 and the MTC device 3-2 are configuredto employ the same CE level for paging (and indeed other communications)the base station's 5 cell. The appropriate CE level may be determined(e.g. based on signal strength or quality) by either the base station 5or the MTC device 3-2 (and notified to the other one). The appropriateCE level is kept synchronised between the base station 5 and the MTCdevice 3-2 (either directly or via the core network 7). Beneficially,the appropriate CE level for a communication device is notified to thecore network (e.g. the MME), and thus when initiating paging the MME isable to instruct the respective paging base station for each cell of aparticular tracking area (TA) to employ an appropriate CE level in thatcell for the MTC device that is being paged.

It will be appreciated that when a communication device to be paged isoperating in the so-called idle state, its location is known to MME on atracking area (TA) basis only (rather than on a cell level). Therefore,the MME instructs all base stations within that TA (including e.g. basestation 5 in FIG. 1) to transmit an appropriately formatted RRC pagingmessage (including a paging record for that communication device in theRRC paging message) by employing the required CE level for their cellwith respect of the paged communication device. The term idle state asused herein refers to an operational mode in which the communicationdevice is currently not sending/receiving user data over its dedicatedradio bearer(s), although its transceiver may be active (e.g. it maystill receive broadcast data, perform signal measurements, and/or thelike).

As with conventional paging a paging occasion (PO) is configured forpaging the MTC devices. Beneficially, however, the PO defines aplurality (‘bundle’) of subframes in a certain subband (e.g. by definingthe start point—or index of the first subframe—of that bundle ofsubframes).

In the examples described in more detail below, the system may employscheduling (e.g. Layer 1 (L1) scheduling) of the paging transmissionsvia the ePDCCH. However, in a particularly beneficial examplecontrol-less paging is used, i.e. paging without requiring associatedresources being scheduled in the ePDCCH. Instead, paging messages aretransmitted over a transmission block of predetermined size (and over apredetermined subband), which can be received by each communicationdevice 3 within the cell of the base station 5.

The bundle of subframes defined by the PO are subframes in which the MTCdevice is to monitor the repetitions of the ePDCCH for paging messagescheduling in the case where the ePDCCH is used to schedule pagingtransmission. The bundle of subframes defined by the PO are subframes inwhich the MTC device is to monitor the repetitions of the PDSCH for apaging message in the case where the ePDCCH is not used for schedulingpaging transmission.

The base station 5 may configure different resources and/or pagingregions per CE level to effectively separate the paging for MTC deviceshaving different CE levels between different respective resources and/orpaging regions. However, in a particularly beneficial example, pagingmessage transmissions are not separated for different coverageenhancement levels (allowing all MTC devices, regardless of CE level, tobenefit from scheduled or control-less paging in the same subband). Inthis case, paging message transmissions may be realised using eitherwith or without ePDCCH.

In summary, the above described communication system supports variousbeneficial options for paging communication devices within the cell ofthe base station, with particular focus on the limitations of MTCdevices. Paging messages can be scheduled dynamically and (ifapplicable) in dependence on the required CE level for each MTC devicewithout (significantly) affecting legacy and/or conventionalcommunication devices in the cell.

<Communication Device>

FIG. 2 is a block diagram illustrating the main components of thecommunication device 3 shown in FIG. 1. The communication device 3 maybe an MTC device or a mobile (or ‘cellular’) telephone configured as amachine-type communication device. The communication device 3 comprisesa transceiver circuit 31 which is operable to transmit signals to, andto receive signals from, the base station 5 via at least one antenna 33.Typically, the communication device 3 also includes a user interface 35which allows a user to interact with the communication device 3, howeverthis user interface 35 may be omitted for some MTC devices.

The operation of the transceiver circuit 31 is controlled by acontroller 37 in accordance with software stored in memory 39. Thesoftware includes, among other things, an operating system 41, acommunications control module 43, a scheduling determination module 44,an MTC module 45, and a paging module 47.

The communications control module 43 controls communications between thecommunication device 3 and the base station 5 and/or other communicationnodes (via the base station 5).

The scheduling determination module 44 monitors transmissions by thebase station 5 in predetermined POs (if applicable) and determineswhether or not the monitored POs include control data for scheduling apaging transmission. If a monitored PO does include such control data,then the scheduling determination module 44 determines the communicationresources (e.g. subframe/subband) associated with the pagingtransmission. In case a control-less is being used, the schedulingdetermination module 44 maintains information identifying the resourcesover which control-less paging messages can be transmitted and instructsthe paging module 47 to decode paging messages transmitted therein.

The MTC module 45 is operable to carry out machine-type communicationtasks. For example, the MTC module 45 may collect data for sending (e.g.periodically and/or upon detecting a trigger) to a remote server (viathe transceiver circuit 31). The MTC module 45 is also responsible forobtaining (determining and/or obtaining from the base station 5) anappropriate CE level to be used in the cell of the base station 5serving the communication device 3.

The paging module 47 receives (over appropriate communication resourcesdetermined by the scheduling module 44) and processes paging messagesaddressed to the communication device 3.

<Base Station>

FIG. 3 is a block diagram illustrating the main components of the basestation 5 shown in FIG. 1. The base station 5 comprises an E-UTRAN basestation (eNB) comprising a transceiver circuit 51 which is operable totransmit signals to, and to receive signals from, the communicationdevices 3 via one or more antennas 53. The base station 5 is alsooperable to transmit signals to and to receive signals from a corenetwork 7 via an appropriate core network interface 55 (such as an S1interface). The operation of the transceiver circuit 51 is controlled bya controller 57 in accordance with software stored in memory 59.

The software includes, among other things, an operating system 61, acommunications control module 63, a paging module 65, a systeminformation module 67, and an MTC support module 69.

The communications control module 53 controls communications with thecommunication devices 3.

The paging module 65 generates and transmits paging messages (via thecommunications control module 63) for communication devices 3 locatedwithin the cell of the base station 5.

The system information module 67 is responsible for broadcasting systeminformation (such as configuration of the cell of the base station 5)and/or other broadcast transmissions for receipt by the communicationdevices 3 located within the cell of the base station 5. For example,the broadcast portion transmits, over appropriate PO(s), paging messages(generated by the paging module 65).

The MTC support module 69 handles (generates, sends, and receives)messages for MTC devices in the cell of the base station 5. The MTCsupport module 69 is responsible for ensuring that each such message istransmitted using the required number of repetitions (in dependence onthe CE level, if configured) and using the appropriate time andfrequency resources (in a given subframe/within the 1.4 MHz bandsupported by the MTC devices). The MTC support module 69 is alsoresponsible for obtaining (determining and/or obtaining from the corenetwork 7) an appropriate CE level to be employed in the cell of thebase station 5 when communicating with the communication device 3.

In the above description, the communication device 3 and the basestation 5 are described for ease of understanding as having a number ofdiscrete modules. Whilst these modules may be provided in this way forcertain applications, for example where an existing system has beenmodified to implement the invention, in other applications, for examplein systems designed with the inventive features in mind from the outset,these modules may be built into the overall operating system or code andso these modules may not be discernible as discrete entities.

<Operation—General>

FIG. 4 illustrates an exemplary way in which paging can be realised inthe communication system 1 shown in FIG. 1. Specifically, in thisexample, paging messages are transmitted over the PDSCH without anyassociated control data (DCI) being transmitted over the (E)PDCCH forscheduling the paging transmissions. Beneficially, the location (e.g.time/frequency resource) and the size of the paging message (e.g.determined by an associated transport block size (TBS)) are configuredvia system information broadcast.

Moreover, the location and/or the size of the paging message may also beupdated via system information broadcast, if necessary. For example, thebase station 5 is able to indicate/adjust the TBS for paging message viathe system information based on at least one of:

-   -   the (current) average MTC paging load in the cell;    -   the number of connected UEs in the cell; and    -   the (measured/determined/estimated) resource usage for the base        station limited to MTC paging).

In addition, other paging related information may also be indicated viathe system information, such as the PO(s) (e.g. a start point thereof inthe ePDCCH/PDSCH) currently configured for the base station's 5 cell. Itwill be appreciated that a different PO(s) may be configured (andbroadcast via the system information) for each category of communicationdevices and/or for each CE level.

<Operation—Paging for System Information Change>

In order to inform the communication devices 3 located within the cellof the base station 5 about a change of the system information (e.g. POconfiguration, paging TBS, channel configuration, and/or the like), thebase station 5 is configured to generate and send an appropriatelyformatted paging message to the communication devices 3. The systeminformation change paging is carried out using a one bit indicator(known as ‘systemInfoModification’ bit) which is transmitted togetherwith other regular (UE specific) paging records, if any. When it isabout to change any system information element, the base station 5transmits this indicator bit on all POs for all communication devices inits cell in order to ensure that each communication device 3 has anopportunity to receive the updated system information without delay.Each communication device receiving (via any PO) a paging message thatincludes the system information change indicator bit proceeds toobtaining the updated system information by listening to the next systeminformation broadcast (e.g. at the boundary of the ‘BCCH modificationperiod’).

It will be appreciated, however, that a system information change may benotified in a different way for communication devices (at least for MTCdevices) operating in the ‘RRC_IDLE’ and in the ‘RRC_CONNECTED’ state.

System Information Change for UEs in RRC_IDLE

It will be appreciated that for communication devices in idle mode, thesystem information modification indicator is transmitted together withnormal paging record(s). In this case, the base station 5 needs to sendthe system information change indicator bit on all POs therebyaddressing all types of communication devices (including MTC devices andlegacy UEs as well).

Optionally, e.g. if system information changes are relatively frequent,paging for system information modification may be separated from normalpaging. In this case, preferably, paging for system information istransmitted in a predetermined common subband (e.g. the centralsubband), and all communication devices need to be configured to work onthis common subband (at least during the PO) and monitor for the systeminformation modification bit in one or more POs of this subband.Consequently, MTC devices cannot be scheduled in other subbands duringthe paging occasions for system modification in the common subband.However, in this case there is no need to include the‘systemInfoModification’ bit in every PO in every subband, albeitrequiring some additional paging monitoring by the MTC devices, whichmight slightly increase their power consumption.

System Information Change for UEs it RRC_CONNECTED

It is likely that communication devices in RRC_CONNECTED mode arescheduled on a subband that is different from the subband for monitoringpaging. In any case, it will be appreciated that the system informationmodification indicator may be transmitted together with normal pagingrecord(s), as above, i.e. the base station 5 needs to send the systeminformation change indicator bit on all POs in every subband in order toreach all types of communication devices. However, this option mayrequire communication devices in RRC_CONNECTED mode to re-tune to theirassociated paging subband in order to obtain the system informationchange notification.

Therefore, in this system, dedicated signalling is used for informingRRC_CONNECTED communication devices (at least MTC devices) about achange in system information. For example, if there is on-going datatransmission for a particular communication device, it is possible tomultiplex the updated system information (at least the changed partthereof) and other data being transmitted to that communication device.Consequently, RRC-CONNECTED communication devices are not required tomonitor their associated PO for system information modification becausethe updated system information is sent via unicast transmission. Thismay result in improved operation of communication devices, especiallyMTC devices that operate over a limited bandwidth.

In another option, it may be possible to force a communication deviceoperating in the RRC_CONNECTED to obtain the system information byreleasing the communication device's RRC connection. This may bebeneficial if, for example, there is no ongoing data transmission tothis communication device (thus the risk of data loss is kept minimal).Once its RRC connection is released, the communication device proceedsto read the system information transmitted via the broadcast channel (asper default procedure).

It will be appreciated that the unicast based option and the RRC releasebased option may be employed together by the base station 5 (dependingon implementation).

<Operation—PO Configurations>

In the current LTE standards, a paging occasion (PO) is defined as asubframe where there may be a P-RNTI transmitted on the PDCCH forscheduling a paging message. A radio frame may contain one to four POs.When DRX is used the UE needs to monitor only one PO per DRX cycle.

In the present system, however, the POs are defined such thatrepetitions for MTC devices are also supported (when appropriate).Specifically, a PO in this system is defined as (the start point of) abundle of subframes in a certain subband where:

-   -   the UE monitors repetitions of ePDCCH for paging message        scheduling in case ePDCCH is needed for paging transmission; or    -   the UE monitors repetitions of PDSCH for paging message in case        ePDCCH is not needed for paging transmission.

Furthermore, there may be different POs for different sub-bands (e.g. tosupport MTC devices with different CE levels).

FIGS. 5 to 8 illustrate further details of various PO configurationoptions and the resulting paging transmissions in this system.

Specifically, the examples shown in FIGS. 5 and 6 illustrate scenarioswhen paging message transmissions are separated for different coverageenhancement levels.

FIG. 5 illustrates paging message transmissions using ePDCCH (eCSS). Inthis example, the scheduling information (e.g. time-frequency resource,MCS/TBS) that allows the MTC device to acquire a paging message on thePDSCH is dynamically indicated by in ePDCCH. In this case, a differentP-RNTI and/or a different eCSS may be used for each CE level.

FIG. 6 illustrates paging message transmissions without using ePDSCH.This solution may also be referred to a ‘control-less’ paging, i.e. thescheduling information (e.g. time-frequency resource, MCS/TBS) thatallows the MTC device to acquire a paging message on the PDSCH is notindicated dynamically by in ePDCCH, but it is predefined or it isindicated in (or forms part of) the system information). In this case,different time and/or frequency resources (within the PDSCH) may beallocated for different CE levels. It will be appreciated that in thePDSCH based scenario shown in FIG. 6, effectively, a control-less pagingmay be realised for each CE level, e.g. as described above withreference to FIG. 4.

In the examples shown in FIGS. 7 and 8, paging message transmissions arenot separated for different coverage enhancement levels. Specifically,FIG. 7 illustrates paging message transmissions with ePDCCH, and FIG. 8illustrates paging message transmissions without ePDCCH (e.g. whenePDCCH is not or cannot be used for paging transmissions). It will beappreciated that in the scenario shown in FIG. 8, effectively, acontrol-less paging may be realised, e.g. as described above withreference to FIG. 4.

<Operation—CE Level Determination>

In the following, a number of options are described for determining anappropriate CE level for a particular MTC device 3-2 in the basestation's 5 cell, and to ensure that the same CE level is employed byboth the MTC device 3-2 and its serving base station 5 in theircommunications with each other.

FIG. 9 illustrates an option in which the serving base station 5(denoted ‘eNB’) is responsible for the decision on which CE level aparticular MTC device (denoted ‘UE’) should employ in a given cell.

As illustrated in step S92, the base station 5 is configured todetermine (using its MTC support module 69) an appropriate CE level forthe MTC device 3-2 based on the random access procedure (denoted ‘PRACH’in FIG. 9) performed between the base station 5 and the MTC device 3-2in the cell of the base station 5 (as generally shown in step S91).

Once the base station 5 has determined the appropriate CE level for theMTC device 3-2, it informs (in step S93) the core network 7 (e.g. theMME/HSS) which stores this information for later use (e.g. for pagingthe MTC device 3-2 via this base station 5).

As generally shown in step S94, the base station 5 may also inform theMTC device 3-2 about the determined CE level for its cell, either in aseparate message or as part of the random access procedure (e.g. stepS94 may form part of step S91). It will be appreciated that the basestation 5 may be configured to inform the MTC device about the CE levelimplicitly, for example, by employing a given number of repetitions(during and/or after the random access procedure) corresponding to thedetermined CE level.

It will be appreciated that there are a number of ways in which the basestation 5 can derive the appropriate CE/repetition level for an MTCdevice, based on the RACH procedure, including for example:

-   -   1) MTC devices with different CE level may use different        preamble resources (with corresponding different repetition        times) in accordance with an appropriate predetermined        relationship mapping between preamble resources and        corresponding CE levels. In this case, the base station can        determine the appropriate CE level based on which preamble        resources (and/or based on the repetition times) used by the MTC        device 3-2. In this case however, optionally, the base station        may also be configured to use a different CE level than the CE        level indicated by the relationship mapping between preamble        resources and corresponding CE levels (e.g. if the base station        5 is able to successfully decode the MTC device's preamble        transmission by combing fewer repetitions than required for that        CE level).

2) Otherwise, if there is no associated preamble resource set configuredfor each different CE level, then the base station 5 may be configuredto determine the coverage level based on a number of repetitionsrequired for successful decoding of the preamble transmitted by the MTCdevice 3-2.

Furthermore, e.g. if the MTC device 3-2 has never been connected to thiscell/or it has not connected to this cell within a predetermined timewindow, then one or more of the following options may also be used:

-   -   3) The base station 5 may be configured to assume the maximum        and/or a default CE/repetition level for the MTC device 3-2 in a        cell in which the MTC device 3-2 has never been connected (or it        has not connected within a predetermined time window).    -   4) If the MTC device 3-2 reselected to a new cell (of the base        station 5), then an appropriate RACH procedure may be triggered        (by the MTC module 45) in order to let the base station 5 detect        the associated CE level of that MTC device 3-2 in the new cell,        otherwise the MTC device 3-2 may not be paged in the new cell        until it has performed a RACH procedure via that cell (although        the MTC device 3-2 is still being paged in other cells) or the        MTC device 3-2 will be paged by assuming the maximum and/or a        default CE/repetition in this new cell.

It will be appreciated that if the required CE level of an MTC devicechanges in a cell (e.g. based on its own estimation), particularly inthe current cell in which the MTC device is currently camping, then anappropriate RACH procedure may be triggered (by the MTC module 45) inorder to let the base station 5 update the associated CE level storedfor the MTC device (for that cell).

Beneficially, therefore, this option allows more control for the basestation 5 in the determination of an appropriate CE level. In this casethe same MTC device may have different CE/repetition levels in differentcells. However, such cell specific CE level can be stored in the corenetwork 7 (MME/HSS), for each MTC device, so that each MTC device can bepaged in any cell using the appropriate CE level (and repetitions)required in that cell. Thus, when the MME initiates paging of the MTCdevice 3-2, in step S95, it includes in its paging request the cellID(s) and the respective associated CE/repetition level for each cell inwhich the MTC device 3-2 is to be paged.

As generally shown in step S96, since both the base station 5 and theMTC device 3-2 employ the same CE level, the base station 5 is operableto transmit (and the MTC device 3-2 is operable to monitor) on thecorrect PO resource corresponding to that CE level. Thus, when in stepS97 the base station 5 transmits a paging message (scheduled via the POin S96) for the MTC device 3-2, it can apply the correct CE level forthat MTC device 3-2 (and employ the required number of repetitions, ifany).

FIG. 10 illustrates an option in which the MTC device 3-2 is responsiblefor the decision on which CE level that MTC device 3-2 employs in agiven cell.

Specifically, in this case the MTC device's 3-2 determination (in stepS102) is based on measurements of the (downlink) radio conditions of anumber of cells (e.g. all detected cells) in the vicinity of the MTCdevice 3-2. It will be appreciated that the MTC device 3-2 may measurethe radio conditions for at least its current serving cell, e.g. thecell of the base station 5.

Once the MTC device 3-2 has determined, in step S102, its appropriate CElevel for a particular cell (or a set of respective CE levels for aplurality of cells), it informs the core network 7 (e.g. the MME/HSS)about the applicable CE level(s) and (optionally) the corresponding cellID(s). It will be appreciated that the MTC device 3-2 may report to theapplicable CE level(s) (corresponding cell ID(s), if any) as part of acapability report (and/or the like).

It will be appreciated that if the MTC device 3-2 determines (e.g. basedon its own estimation/signal quality measurements) that the required CElevel (in at least one cell) has changed, particularly in the currentcell in which the MTC device 3-2 is currently camping, then the MTCdevice 3-2 may notify the core network 7 and update the associated CElevel stored for the MTC device (for the at least one cell in which theCE level has changed).

It will be appreciated that the MTC device 3-2 may be configured toreport/update the CE level when one or more of the following conditionsare met: i) the MTC device performs an attach procedure; ii) the MTCdevice has found a new neighbour cell as paging cell; and iii) the MTCdevice determines a change in the required CE level and/or a change inradio conditions in a cell.

The core network 7 stores this information for later use (e.g. forpaging the MTC device 3-2 in step S105). Steps S105 to S107 correspondto steps S95 to S97 described above, thus their description is omittedherein for simplicity.

A benefit associated with this option is that the required CE levels fora plurality of cells (including e.g. potential paging cells for the MTCdevice 3-2) can be measured and reported to core network 7 at once.

<Modifications and Alternatives>

Detailed exemplary embodiments have been described above. As thoseskilled in the art will appreciate, a number of modifications andalternatives can be made to the above exemplary embodiments whilst stillbenefiting from the inventions embodied therein.

In the above description, repetition in time domain is assumed for alltransmissions. However, such repetitions are omitted in FIGS. 4 to 10for simplicity.

A number of options have been described above, with reference to FIGS. 5to 8. It will be appreciated that these options are not mutuallyexclusive and any of the options may be combined within the same system,either within a single cell and/or in neighbouring cells. For example,the base station may be configured to change from one operation mode toanother, e.g. periodically, in dependence on the number/type of MTCdevices in its cell, in dependence on the overall load in the cell, independence on the type of communication (e.g. broadcast/unicast), and/orthe like.

It will be appreciated that although the communication system isdescribed in terms of the base station operating as a E-UTRAN basestation (eNB), the same principles may be applied to base stationsoperating as macro or pico base stations, femto base stations, relaynodes providing elements of base station functionality, home basestations (HeNB), or other such communication nodes.

In the above exemplary embodiments, an LTE telecommunications system wasdescribed. As those skilled in the art will appreciate, the techniquesdescribed in the present application can be employed in othercommunications systems, including earlier 3GPP type systems. Othercommunications nodes or devices may include user devices such as, forexample, personal digital assistants, laptop computers, web browsers,etc.

In the exemplary embodiments described above, the base station and thecommunication device each include transceiver circuit. Typically, thiscircuitry will be formed by dedicated hardware circuits. However, insome exemplary embodiments, part of the transceiver circuitry may beimplemented as software run by the corresponding controller.

In the above exemplary embodiments, a number of software modules weredescribed. As those skilled in the art will appreciate, the softwaremodules may be provided in compiled or un-compiled form and may besupplied to the base station or the user device as a signal over acomputer network, or on a recording medium. Further, the functionalityperformed by part or all of this software may be performed using one ormore dedicated hardware circuits.

It will be appreciated that the base station may comprise: means forreceiving, from a core network entity, a paging request for paging atleast one MTC device; means for determining a paging occasion when saidat least one MTC device will be sent paging related information, whereinsaid paging occasion identifies a plurality of subframes in which saidpaging related information will be first sent and then repeated; andmeans for sending, and then repeating, said paging related informationin said plurality of subframes identified by said paging occasion.

The paging related information may comprise scheduling informationidentifying time and/or frequency resources to be used for sending apaging message to said at least one MTC device, and said plurality ofsubframes identified by said paging occasion may be subframes in which acontrol channel carrying said paging related information will be sent.

The at least one MTC device may comprise at least one coverage enhancedMTC device having a first coverage enhancement level and at least onecoverage enhanced MTC device having a second coverage enhancement levelthat is different to said first coverage enhancement level.

In this case, the paging related information may comprise a first pagingidentifier (e.g. a radio network temporary identifier) for identifyingpaging related information for said at least one coverage enhanced MTCdevice having a first coverage enhancement level, and a second pagingidentifier (e.g. a different radio network temporary identifier) foridentifying paging related information for said at least one coverageenhanced MTC device having a second coverage enhancement level.

The paging related information for said at least one coverage enhancedMTC device having a first coverage enhancement level may be first sentin a control channel in a first subframe, and paging related informationfor said at least one coverage enhanced MTC device having a secondcoverage enhancement level may be first sent in a control channel in asecond sub-frame that is different to said first subframe.

The paging related information for said at least one coverage enhancedMTC device having a first coverage enhancement level may be sent in acontrol channel in at least one subframe in which paging relatedinformation for said at least one coverage enhanced MTC device having asecond coverage enhancement level is also sent using the same controlchannel.

The paging related information may comprise at least one paging messagefor said at least one MTC device, and said plurality of subframesidentified by said paging occasion may be subframes in which said atleast one paging message will be sent and then repeated. In this case,the base station may further comprise means for sending, to said atleast one MTC device, scheduling information for identifying resourcesto be used for sending said at least one paging message, in a systeminformation block. For example, the scheduling information may compriseinformation identifying a transport block size ‘TBS’ for said requestedpaging.

The at least one MTC device may comprise at least one coverage enhancedMTC device having a first coverage enhancement level and at least onecoverage enhanced MTC device having a second coverage enhancement levelthat is different to said first coverage enhancement level.

In this case, the paging message for said at least one coverage enhancedMTC device having a first coverage enhancement level may be sent using afirst predetermined frequency resource, and a paging message for said atleast one coverage enhanced MTC device having a second coverageenhancement level may be sent using a second predetermined frequencyresource that is different to said first predetermined frequencyresource.

The paging message for said at least one coverage enhanced MTC devicehaving a first coverage enhancement level may be first sent in a datachannel in a first subframe, and a paging message for said at least onecoverage enhanced MTC device having a second coverage enhancement levelmay be first sent in a data channel in a second subframe that isdifferent to said first subframe.

The paging message for said at least one coverage enhanced MTC devicehaving a first coverage enhancement level may be sent in a data channelin at least one subframe in which a paging message for said at least onecoverage enhanced MTC device having a second coverage enhancement levelis also sent in the same data channel.

If the at least one MTC device comprises at least one coverage enhancedMTC device, then said base station may further comprise means foridentifying a coverage enhancement level associated with said at leastone coverage enhanced MTC device, and said means for sending, and thenrepeating, said paging related information may be configured to repeatsending said paging related information for a number of repetitionsdefined by said coverage enhancement level.

The paging request may comprise information identifying said coverageenhancement level and wherein said means for identifying a coverageenhancement level associated with said at least one coverage enhancedMTC device is configured to identify said coverage enhancement levelbased on said information identifying said coverage enhancement level insaid paging request.

The means for identifying a coverage enhancement level associated withsaid at least one coverage enhanced MTC device may be configured toidentify said coverage enhancement level based on information (e.g. arandom access preamble sequence index) obtained during a procedure toset up a random access channel (RACH) with said at least one coverageenhanced MTC device.

If a respective coverage enhancement level cannot be determined for saidat least one coverage enhanced MTC device, then said means for sending,and then repeating, said paging related information may be configured torepeat sending said paging related information for a number ofrepetitions defined in accordance with a predetermined (e.g. a maximumand/or default) coverage enhancement level.

In the above exemplary embodiments, machine-type communication devicesand mobile telephones are described. However, it will be appreciatedthat mobile telephones (and similar user equipment) may also beconfigured to operate as machine-type communication devices. Forexample, the mobile telephone 3-1 may include (and/or provide thefunctionality of) the MTC module 45.

Examples of MTC Applications

It will be appreciated that each communication device may support one ormore MTC applications. Some examples of MTC applications are listed inthe following table (source: 3GPP TS22.368 V13.1.0, Annex B). This listis not exhaustive and is intended to be indicative of the scope ofmachine-type communication applications.

TABLE 1 Service Area MTC applications Security Surveillance systemsBackup for landline Control of physical access (e.g. to buildings)Car/driver security Tracking & Tracing Fleet Management Order ManagementPay as you drive Asset Tracking Navigation Traffic information Roadtolling Road traffic optimisation/steering Payment Point of salesVending machines Gaming machines Health Monitoring vital signsSupporting the aged or handicapped Web Access Telemedicine points Remotediagnostics Remote Maintenance/Control Sensors Lighting Pumps ValvesElevator control Vending machine control Vehicle diagnostics MeteringPower Gas Water Heating Grid control Industrial metering ConsumerDevices Digital photo frame Digital camera eBook

Various other modifications will be apparent to those skilled in the artand will not be described in further detail here.

The following is a detailed description of the way in which the presentinventions may be implemented in the currently proposed 3GPP standard.Whilst various features are described as being essential or necessary,this may only be the case for the proposed 3GPP standard, for exampledue to other requirements imposed by the standard. These statementsshould not, therefore, be construed as limiting the present invention inany way.

Title: Paging for Rel-13 MTC UE

1. Introduction

The repetition is widely needed for both broadcast and unicast channelswhich address to MTCe UE including low complexity UE in normal coverageand in coverage enhancement, so paging transmission procedure needs tobe re-designed for Rel-13 MTCe UE.

In this contribution, we share our views on the following issues:

-   -   1. Whether dynamic L1 scheduling i.e. ePDCCH is needed for        paging transmission?    -   2. How to do the paging for system information change?    -   3. Are the paging messages transmissions separated or not for        different types of Rel13 MTC UEs?    -   4. How to determine the CE/repetition level of a UE for paging        transmission?

2. Discussion

In current specification TS 36.304, one Paging Occasion (PO) is asubframe where there may be P-RNTI transmitted on PDCCH addressing thepaging message. One Radio Frame contains one or more Paging Occasion(s).When DRX is used the UE needs only to monitor one PO per DRX cycle.

In the context of Rel-13 MTC, since repetition will be needed, PO is notone subframe anymore. We propose to adopt following definition of PO:

Proposal 1: Paging Occasion (PO) is the (start point of) a bundle ofsubframes in a certain sub-band where:

-   -   The monitors the repetitions of ePDCCH for paging message        scheduling in case ePDCCH is needed for paging transmission, or    -   The UE monitors the repetitions of PDSCH for paging message in        case ePDCCH is not needed for paging transmission.

We may have different PO on different sub-bands.

2.1 Paging for System Information Chance

As we know, the paging message is also used to inform UEs in RRC_IDLEand UEs in RRC_CONNECTED about a system information change. The systeminformation change paging is one bit indicator and transmitted togetherwith other normal paging records if any. When it is about to change anysystem information element, eNB has to transmit this indicator on allPOs for all UEs to guarantee all UEs will be informed in time.

In the context of Rel-13 MTC, let's discuss system informationmodification for UEs in RRC-IDLE and RRC-CONNECTED mode separately:

System information change for UEs in RRC_IDLE

Option 1: Paging for System Information Modification is TransmittedTogether with Normal Paging Records (as Legacy)

With this option, eNB has to send the paging on all POs addressing toall types of Rel-13 MTC UEs as legacy. The effort to send on all POs ismuch bigger than legacy due to hundreds of repetitions.

Option 2: Paging for System Information Modification is Separated fromNormal Paging

With this option, the paging for system information has to betransmitted in a common sub-band, and all UEs shall work on this commonsub-band and try to monitor the paging occasions for system informationmodification. This means all Rel-13 MTC UEs cannot be scheduled in othersub-band during the paging occasions for system modification. Moreoverthis would be additional paging monitoring work from UE perspective, andlead to more power consumption.

Considering the system information change will be very rare, we slightlyprefer option 1:

Proposal: System information modification indicator is transmittedtogether with normal paging record(s).

System Information Change for UEs in RRC_CONNECTED

Option 1: Notification of the System Information Change Via Paging (asLegacy)

It is likely that UE in RRC_CONNECTED mode is scheduled on a sub-banddifferent from the sub-band for monitoring paging. This will require UEto re-tune to the sub-band for paging and for the system informationreading.

Option 2: Send the New System Information Via Dedicated Signalling:

UE can keep working on the sub-band for unicast channels. If there is alarge amount of rel13 UE in RRC-CONNECTED, it will be very costly tosend the changed system information one UE by one UE. However if thereis on-going data transmission to the target UE, by multiplexing thesystem information and the data, it will be less costly provided onlychanged part of SI will be sent to UE.

Option 3: Release RRC Connection

If there is no ongoing data transmission to a UE, then another possiblechoice is to release this UE, hence the UE will read the systeminformation via broadcast channel.

Option 2 and option 3 can work together by eNB implementation.Considering the UE in coverage enhancement will be kept in RRC-CONNECTEDmode only if there is on-going data, it is propose:

Proposal: Dedicated signalling will be used for system informationchange for RRC-CONNECTED REL13 MTC UEs, i.e. RRC-CONNECTED REL13 MTC UEsare not required to monitoring paging for system informationmodification.

2.2 With or without ePDCCH

Similar to system information transmission, one key question regardingpaging transmission is whether dynamic L1 scheduling information inePDCCH is needed or not, we have pros and cons analysis as below:

Without ePDCCH (i.e. without dynamic L1 scheduling information):

-   -   Lack of scheduling flexibility: the radio resource for paging        transmissions, modulation order, coding rate cannot be changed        dynamically.    -   Fixed TBS/MCS and Radio Resource: fixed number (e.g. only 1) of        UE can be paged in one PO.    -   Extra paging delay if there is no space to accommodate all        paging requests: when more UE needs to be paged, eNB could delay        the paging to next PO, this will cause scheduling delay.    -   Paging capacity limit due to the fixed TBS, on the other hand,        more POs can be configured to increase the paging capacity,        however it will cause more UE power consumption to monitor more        POs.    -   Save the resource use for ePDCCH transmission.

With ePDCCH (i.e. with dynamic L1 scheduling information)

-   -   More scheduling flexibility: the radio resource for paging        transmissions, modulation order, coding rate can be changed        dynamically    -   Changeable TBS/MCS and Radio Resource: number of UEs paged in        one PO is flexible.    -   Paging capacity is adaptive to the paging request.    -   More radio resource used for ePDCCH transmission.    -   Double power consumption: for each PO, UE has to monitor ePDCCH        bundle first and then the PDSCH bundle if ePDCCH with P-RNTI        detected (this is very likely). This means double power        consumption in maximum due to the ePDCCH-PDSCH two-step paging        monitoring

Comparing “without ePDCCH” option, “with ePDCCH” option has obviousflexibility in term of scheduling, paging capacity and is more adaptive.However it is not clear it will be more resource efficient thinkingextra resource required for ePDCCH repetitions. Also it will result inmuch more awake time and increased power consumption from UE point ofview. A compromised way is to allow limited flexibility on top of theoption “without ePDCCH”, e.g. to indicate/adjust the TB size of pagingmessage in system information based on e.g. MTC paging load of the cell.

Proposal: RAN2 consider to not have dynamic L1 scheduling information inePDCCH but indicate limited scheduling information e.g. TBS in S1 forpaging transmission.

2.3 Separated or not

RAN1 agreed that the paging messages for Rel-13 low-complexity UEsand/or UEs operating in coverage enhancements (CE) are transmittedseparately from paging messages for other UEs. It has not been confirmedwhether paging messages for Rel-13 low-complexity UEs operating innormal coverage and operating in different coverage enhancements (CE)are transmitted separately or not.

In the following discussion, we do not particularly mention LC Rel-13MTC UE in normal coverage. Low complexity UE in normal coverage can beconsidered as one special repetition/CE level e.g. CE level 0, since UEposition is unknown for NW, so cell edge coverage is assumed whencalculating the repartition times.

If they are separated: For each CE level, separated ePDCCH/PDSCHtransmission is needed. When there is one paging targeting a UE in CElevel 1 and another paging targeting a UE in CE level 2, two ePDCCH isneeded if ePDCCH is there, or two PDSCHs are needed if ePDCCH is notthere. There may be more PDSCH load due to separate padding fordifferent TBs. Regarding system information modification, eNB has tosend paging/paging scheduling on all POs corresponding to all repetitionlevels, and this also means more resource consumption. UE and networkside shall strictly have the same assumption on the repetition level inall situations, otherwise, it will result in misalignment betweentransmission and monitoring resource, and then paging will always fail.

If they are not separated: As shown in figure, repetition times shouldbe the maximum value required by all paged UEs. When there is one pagingtargeting a UE in CE level 1 requiring N times of repetitions andanother paging targeting a UE in CE level 4 requiring M times ofrepetitions, wherein M>N, eNB will transmit the paging message includingboth paging records of these two UEs with M times of repetitions. In thecontrol of eNB implementation, when the repetition times between pagedUEs are too much different, and there are many paging requests, UE cangroup the similar CE level UEs' pagings together and page differentgroups in different time at the cost of extra paging delay. From UEpoint of view, Different CE level UEs try to combine ePDCCH/PDSCH onenough number of sub frames. Follow the same example, UE in CE level 1try to decode the combination of N subframes ePDCCH/PDSCH, but UE in CElevel 4 try to decode the combination of M subframes ePDCCH/PDSCH tocheck if it is paged. If there is only small amount of paging requests,it might be more resource efficient by multiplexing paging records eventhough they have very different repetition times. There will be lessresource consumption for paging of system information modification.

If ePDCCH is there, for the “separated option”, even though differentePDCCH is needed for different CE levels, it is still possible tomultiplex paging records addressing to different CE level into onePDSCH/TB, in a way that all ePDCCHs point to the same PDSCH.

We slightly prefer not to separate the paging transmission for differenttype of Rel-13 MTC UEs based on above analysis:

Proposal: not to separate the paging transmissions for different type ofRel-13 MTC UEs, i.e. Network may transmit paging records addressing todifferent type/CE level Rel-13 MTC UEs in one paging message.

2.4 CE Level Determination

To determine the CE level of UE in a certain cell, there are twooptions:

Option 1: eNB-Based [as Shown in FIG. 9]

eNB makes the final decision on which CE level the UE is in a givencell, and then inform CN and also maybe inform UE to align theunderstanding. This option allows more control in eNB side. The same UEpossibly has different CE/repetition level in different cell, and inorder to allow to page a UE in more than one cells as we have today, theCE levels in all cells have to be collected one by one based on RACHprocedure.

Option 2: UE-Based [as Shown in FIG. 10]

UE measures the DL radio condition of all detected cells, and determinethe CE levels in each cells, and then report to CN e.g. as part ofcapability report. eNB has less control with this option, we have tomake sure the UE will not abuse this and report higher CE level than itneeds. The CE levels in all paging cells can be measured and reported inone shot to network.

Proposal: RAN2 discuss whether the CE level determination is UE based oreNB based.

The whole or part of the exemplary embodiments disclosed above can bedescribed as, but not limited to, the following supplementary note.

(Supplementary note 1) A base station for a communication system inwhich machine type communication ‘MTC’ devices communicate via said basestation, the base station comprising:

means for receiving, from a core network entity, a paging request forpaging at least one MTC device:

means for determining a paging occasion when said at least one MTCdevice will be sent paging related information, wherein said pagingoccasion identifies a plurality of subframes in which said pagingrelated information will be first sent and then repeated; and

means for sending, and then repeating, said paging related informationin said plurality of subframes identified by said paging occasion.

(Supplementary note 2) The base station according to Supplementary note1, wherein said paging related information comprises schedulinginformation identifying time and/or frequency resources to be used forsending a paging message to said at least one MTC device, and whereinsaid plurality of subframes identified by said paging occasion aresubframes in which a control channel carrying said paging relatedinformation will be sent.

(Supplementary note 3) The base station according to Supplementary note2, wherein said at least one MTC device comprises at least one coverageenhanced MTC device having a first coverage enhancement level and atleast one coverage enhanced MTC device having a second coverageenhancement level that is different to said first coverage enhancementlevel.

(Supplementary note 4) The base station according to Supplementary note3, wherein said paging related information comprises a first pagingidentifier (e.g. a radio network temporary identifier) for identifyingpaging related information for said at least one coverage enhanced MTCdevice having a first coverage enhancement level, and a second pagingidentifier (e.g. a different radio network temporary identifier) foridentifying paging related information for said at least one coverageenhanced MTC device having a second coverage enhancement level.

(Supplementary note 5) The base station according to Supplementary note3, wherein paging related information for said at least one coverageenhanced MTC device having a first coverage enhancement level is firstsent in a control channel in a first subframe, and paging relatedinformation for said at least one coverage enhanced MTC device having asecond coverage enhancement level is first sent in a control channel ina second sub-frame that is different to said first subframe.

(Supplementary note 6) The base station according to Supplementary note3, wherein paging related information for said at least one coverageenhanced MTC device having a first coverage enhancement level is sent ina control channel in at least one subframe in which paging relatedinformation for said at least one coverage enhanced MTC device having asecond coverage enhancement level is also sent using the same controlchannel.

(Supplementary note 7) The base station according to Supplementary note1, wherein said paging related information comprises at least one pagingmessage for said at least one MTC device, and wherein said plurality ofsubframes identified by said paging occasion are subframes in which saidat least one paging message will be sent and then repeated.

(Supplementary note 8) The base station according to Supplementary note7, wherein said base station further comprises means for sending, tosaid at least one MTC device, scheduling information for identifyingresources to be used for sending said at least one paging message, in asystem information block.

(Supplementary note 9) The base station according to Supplementary note8, wherein said scheduling information comprises information identifyinga transport block size ‘TBS’ for said requested paging.

(Supplementary note 10) The base station according to any ofSupplementary notes 7 to 9, wherein said at least one MTC devicecomprises at least one coverage enhanced MTC device having a firstcoverage enhancement level and at least one coverage enhanced MTC devicehaving a second coverage enhancement level that is different to saidfirst coverage enhancement level.

(Supplementary note 11) The base station according to Supplementary note10, wherein a paging message for said at least one coverage enhanced MTCdevice having a first coverage enhancement level is sent using a firstpredetermined frequency resource, and a paging message for said at leastone coverage enhanced MTC device having a second coverage enhancementlevel is sent using a second predetermined frequency resource that isdifferent to said first predetermined frequency resource.

(Supplementary note 12) The base station according to Supplementary note10, wherein a paging message for said at least one coverage enhanced MTCdevice having a first coverage enhancement level is first sent in a datachannel in a first subframe, and a paging message for said at least onecoverage enhanced MTC device having a second coverage enhancement levelis first sent in a data channel in a second subframe that is differentto said first subframe.

(Supplementary note 13) The base station according to Supplementary note10, wherein a paging message for said at least one coverage enhanced MTCdevice having a first coverage enhancement level is sent in a datachannel in at least one subframe in which a paging message for said atleast one coverage enhanced MTC device having a second coverageenhancement level is also sent in the same data channel.

(Supplementary note 14) The base station according to any ofSupplementary notes 1 to 9, wherein said at least one MTC devicecomprises at least one coverage enhanced MTC device, wherein said basestation further comprises means for identifying a coverage enhancementlevel associated with said at least one coverage enhanced MTC device,and wherein said means for sending, and then repeating, said pagingrelated information is configured to repeat sending said paging relatedinformation for a number of repetitions defined by said coverageenhancement level.

(Supplementary note 15) The base station according to Supplementary note14, wherein said paging request comprises information identifying saidcoverage enhancement level and wherein said means for identifying acoverage enhancement level associated with said at least one coverageenhanced MTC device is configured to identify said coverage enhancementlevel based on said information identifying said coverage enhancementlevel in said paging request.

(Supplementary note 16) The base station according to Supplementary note14, wherein said means for identifying a coverage enhancement levelassociated with said at least one coverage enhanced MTC device isconfigured to identify said coverage enhancement level based oninformation (e.g. a random access preamble sequence index) obtainedduring a procedure to set up a random access channel (RACH) with said atleast one coverage enhanced MTC device.

(Supplementary note 17) The base station according to Supplementary note14, wherein if a respective coverage enhancement level cannot bedetermined for said at least one coverage enhanced MTC device, then saidmeans for sending, and then repeating, said paging related informationis configured to repeat sending said paging related information for anumber of repetitions defined in accordance with a predetermined (e.g. amaximum and/or default) coverage enhancement level.

(Supplementary note 18) A base station for a communication system inwhich machine type communication ‘MTC’ devices communicate via said basestation, the base station comprising:

means for receiving, from a core network entity, a paging request forpaging at least one MTC device:

means for determining a paging occasion when said at least one MTCdevice will be sent a paging message;

means for sending, to said at least one MTC device, schedulinginformation for identifying resources to be used for sending said pagingmessage, in a system information block;

means for sending, to said at least one MTC device, said paging messageusing said resources in accordance with said paging occasion.

(Supplementary note 19) A base station for a communication system inwhich machine type communication ‘MTC’ devices communicate via said basestation, the base station comprising:

means for receiving, from a core network entity, a paging request forpaging at least one coverage enhanced MTC device;

means for identifying a coverage enhancement level associated with saidat east one coverage enhanced MTC device; and

means for sending paging related information and then repeating sendingsaid paging related information for a number of repetitions defined bycoverage enhancement level.

(Supplementary note 20) A base station for a communication system inwhich machine type communication ‘MTC’ devices communicate via said basestation, the base station comprising:

means for determining that there is a requirement to notify said MTCdevices that there has been a change in system information resulting inmodified system information;

means for notifying any idle mode MTC devices that there has been achange in system information by sending a notification together with anypaging records for said MTC devices using a paging message; and

means for providing any radio resource control ‘RRC’ connected mode MTCdevices with at least a modified part of the modified system informationusing MTC device dedicated signalling (e.g. unicast/dedicated RRCsignalling).

(Supplementary note 21) A machine type communication ‘MTC’ device forcommunicating with a base station, the MTC device comprising:

means for determining a paging occasion when said base station may sendpaging related information, wherein said paging occasion identifies aplurality of subframes in which said paging related information will befirst sent and then repeated by said base station; and

means for receiving said paging related information in said plurality ofsubframes identified by said paging occasion.

(Supplementary note 22) A machine type communication ‘MTC’ device for acommunication system in which machine type communication ‘MTC’ devicescommunicate via a base station, the MTC device comprising:

means for obtaining, from a system information block broadcast by saidbase station, scheduling information for identifying resources to beused for sending at least one paging message;

means for determining a paging occasion when said base station may senda paging message for said MTC device;

means for determining, from said scheduling information said resourcesto be used for sending at least one paging message; and

means for receiving said paging message using said resources inaccordance with said paging occasion.

(Supplementary note 23) A machine type communication ‘MTC’ device for acommunication system in which MTC devices communicate via a basestation, the MTC device comprising:

means for performing measurements for establishing a measure of a signalquality associated with at least one cell;

means for determining, based on said measure of a signal qualityassociated with at least one cell, a respective coverage enhancementlevel associated with said at least one cell; and

means for sending said respective coverage enhancement level associatedwith said at least one cell to said base station.

(Supplementary note 24) A machine type communication ‘MTC’ device for acommunication system in which MTC devices communicate via a basestation, the MTC device comprising:

means for forming a radio resource control ‘RRC’ connection with saidbase station to enter an RRC connected mode;

a transceiver configured to obtain, using dedicated signalling (e.g.unicast/dedicated RRC signalling), (at least a modified part of)modified system information associated with a cell of the base station,when in said RRC connected mode.

(Supplementary note 25) A core network node (e.g. a mobility managemententity) for a communication system, the core network node comprising:

means for obtaining information identifying a coverage enhancement levelrequired in a cell of a base station for at least one coverage enhancedMTC device;

means for generating a paging request for paging said at least onecoverage enhanced MTC device via said base station, wherein said pagingrequest includes said information identifying said coverage enhancementlevel required in said cell of a base station for said at least onecoverage enhanced MTC device; and

means for sending said paging request to said base station for pagingsaid at least one coverage enhanced MTC device in said cell inaccordance with said coverage enhancement level required in said cell.

(Supplementary note 26) A system comprising the base station accordingto any of Supplementary notes 1 to 20, the MTC device according to anyof Supplementary notes 21 to 24, and the core network node according toSupplementary note 25.

(Supplementary note 27) A method performed by a base station in acommunication system in which machine type communication ‘MTC’ devicescommunicate via said base station, the method comprising:

receiving, from a core network entity, a paging request for paging atleast one MTC device;

determining a paging occasion when said at least one MTC device will besent paging related information, wherein said paging occasion identifiesa plurality of subframes in which said paging related information willbe first sent and then repeated; and

sending, and then repeating, said paging related information in saidplurality of subframes identified by said paging occasion.

(Supplementary note 28) A method performed by a base station for acommunication system in which machine type communication ‘MTC’ devicescommunicate via said base station, the method comprising:

receiving, from a core network entity, a paging request for paging atleast one MTC device;

determining a paging occasion when said at least one MTC device will besent a paging message; sending, to said at least one MTC device,scheduling information for identifying resources to be used for sendingsaid paging message, in a system information block;

sending, to said at least one MTC device, said paging message using saidresources in accordance with said paging occasion.

(Supplementary note 29) A method performed by a base station for acommunication system in which machine type communication ‘MTC’ devicescommunicate via said base station, the method comprising:

receiving, from a core network entity, a paging request for paging atleast one coverage enhanced MTC device;

identifying a coverage enhancement level associated with said at leastone coverage enhanced MTC device; and

sending paging related information and then repeating sending saidpaging related information for a number of repetitions defined bycoverage enhancement level.

(Supplementary note 30) A method performed by a base station for acommunication system in which machine type communication ‘MTC’ devicescommunicate via said base station, the method comprising:

determining that there is a requirement to notify said MTC devices thatthere has been a change in system information resulting in modifiedsystem information;

notifying any idle mode MTC devices that there has been a change insystem information by sending a notification together with any pagingrecords for said MTC devices using a paging message; and

providing any radio resource control ‘RRC’ connected mode MTC deviceswith at least a modified part of the modified system information usingMTC device dedicated signalling (e.g. unicast/dedicated RRC signalling).

(Supplementary note 31) A method performed by a machine typecommunication ‘MTC’ device for communicating with a base station, themethod comprising:

determining a paging occasion when said base station may send pagingrelated information, wherein said paging occasion identifies a pluralityof subframes in which said paging related information will be first sentand then repeated by said base station; and

receiving said paging related information in said plurality of subframesidentified by said paging occasion.

(Supplementary note 32) A method performed by a machine typecommunication ‘MTC’ device in a communication system in which machinetype communication ‘MTC’ devices communicate via a base station, themethod comprising:

obtaining, from a system information block broadcast by said basestation, scheduling information for identifying resources to be used forsending at least one paging message;

determining a paging occasion when said base station may send a pagingmessage for said MTC device;

determining, from said scheduling information said resources to be usedfor sending at least one paging message; and

receiving said paging message using said resources in accordance withsaid paging occasion.

(Supplementary note 33) A method performed by a machine typecommunication ‘MTC’ device in a communication system in which MTCdevices communicate via a base station, the method comprising:

performing measurements for establishing a measure of a signal qualityassociated with at least one cell;

determining, based on said measure of a signal quality associated withat least one cell, a respective coverage enhancement level associatedwith said at least one cell; and

sending said respective coverage enhancement level associated with saidat least one cell to said base station.

(Supplementary note 34) A method performed by a machine typecommunication ‘MTC’ device in a communication system in which MTCdevices communicate via a base station, the method comprising:

forming a radio resource control ‘RRC’ connection with said base stationto enter an RRC connected mode; and

obtaining, using dedicated signalling (e.g. unicast/dedicated RRCsignalling), (at least a modified part of) modified system informationassociated with a cell of the base station, when in said RRC connectedmode.

(Supplementary note 35) A method performed by a core network node (e.g.a mobility management entity) for a communication system, the methodcomprising:

obtaining information identifying a coverage enhancement level requiredin a cell of a base station for at least one coverage enhanced MTCdevice;

generating a paging request for paging said at least one coverageenhanced MTC device via said base station, wherein said paging requestincludes said information identifying said coverage enhancement levelrequired in said cell of a base station for said at least one coverageenhanced MTC device; and

sending said paging request to said base station for paging said atleast one coverage enhanced MTC device in said cell in accordance withsaid coverage enhancement level required in said cell.

(Supplementary note 36) A computer implementable instructions productcomprising computer implementable instructions for causing aprogrammable communications device to perform the method of any ofSupplementary notes 27 to 35.

This application is based upon and claims the benefit of priority fromUnited Kingdom Patent Application No. 1506156.7, filed on Apr. 10, 2015,the disclosure of which is incorporated herein in its entirety byreference.

The invention claimed is:
 1. A base station for a communication systemin which machine type communication ‘MTC’ devices communicate via saidbase station, the base station comprising: a transceiver and at leastone processor, wherein the at least one processor is configured to:determine whether to notify said MTC devices that there has been asystem information update; notify any idle mode MTC devices about thesystem information update by sending, in a first period comprising aplurality of subframes, a notification using a paging message includinga system information modification indication; provide any idle mode MTCdevices with updated system information in a second period comprising aplurality of subframes subsequent to said first period; and initiate aprocedure for providing a radio resource control ‘RRC’ connected modeMTC device with updated system information using dedicated signalling.2. The base station according to claim 1, wherein said MTC device is abandwidth reduced user equipment (UE).
 3. The base station according toclaim 1, wherein said MTC device is a low complexity user equipment(UE).
 4. The base station according to claim 1, wherein said MTC deviceis a coverage enhanced (CE) user equipment (UE).
 5. The base stationaccording to claim 1, the at least one processor further beingconfigured to determine a paging occasion when at least one MTC devicewill be sent paging related information on an associated physicaldownlink control channel, wherein said paging occasion is a startingsubframe of a number of repetitions of said physical downlink controlchannel.
 6. The base station according to claim 5, wherein thetransceiver is configured to send said paging related information onsaid physical downlink control channel in said starting subframe andthen repeat said paging related information in said repetitions of saidphysical downlink control channel.
 7. The base station according toclaim 5, wherein said paging related information comprises a pagingradio network temporary identifier (P-RNTI).
 8. The base stationaccording to claim 7, wherein said paging related information comprisesa first P-RNTI for at least one coverage enhanced MTC device having afirst coverage enhancement level, and a different P-RNTI for at leastone coverage enhanced MTC device having a second coverage enhancementlevel.
 9. The base station according to claim 5, wherein paging relatedinformation for at least one coverage enhanced MTC device having a firstcoverage enhancement level is first sent in a control channel in a firstsubframe, and paging related information for at least one coverageenhanced MTC device having a second coverage enhancement level is firstsent in a control channel in a second sub-frame that is different tosaid first subframe.
 10. The base station according to claim 5, whereinpaging related information for at least one coverage enhanced MTC devicehaving a first coverage enhancement level is sent in a control channelin at least one subframe in which paging related information for atleast one coverage enhanced MTC device having a second coverageenhancement level is also sent using the same control channel.
 11. Thebase station according to claim 1, wherein said transceiver isconfigured to send, to at least one MTC device, scheduling informationfor identifying resources to be used for sending at least one pagingmessage, in a system information block.
 12. The base station accordingto claim 1, wherein said transceiver is configured to send a pagingmessage for at least one coverage enhanced MTC device having a firstcoverage enhancement level using a first predetermined frequencyresource, and to send a paging message for at least one coverageenhanced MTC device having a second coverage enhancement level using asecond predetermined frequency resource that is different to said firstpredetermined frequency resource.
 13. A machine type communication ‘MTC’device for a communication system in which MTC devices communicate via abase station, the MTC device comprising: at least one processorconfigured to establish a radio resource control ‘RRC’ connection withsaid base station to enter an RRC connected mode; and a transceiverconfigured to obtain, as part of a base station initiated procedure,using dedicated signalling, system information associated with a cell ofthe base station, when in said RRC connected mode, wherein, when the MTCdevice is in idle mode, the transceiver is further configured to: obtaina notification about a system information update in a first periodcomprising a plurality of subframes, using a paging message including asystem information modification indication; and obtain updated systeminformation in a second period comprising a plurality of subframessubsequent to said first period.
 14. A method performed by a basestation for a communication system in which machine type communication‘MTC’ devices communicate via said base station, the method comprising:determining whether to notify said MTC devices that there has been asystem information update; notifying any idle mode MTC devices about thesystem information update by sending, in a first period comprising aplurality of subframes, a notification using a paging message includinga system information modification indication; providing any idle modeMTC devices with updated system information in a second periodcomprising a plurality of subframes subsequent to said first period; andinitiating a procedure for providing a radio resource control ‘RRC’connected mode MTC device with updated system information usingdedicated signalling.
 15. A method performed by a machine typecommunication ‘MTC’ device in a communication system in which MTCdevices communicate via a base station, the method comprising:establishing a radio resource control ‘RRC’ connection with said basestation to enter an RRC connected mode; obtaining, as part of a basestation initiated procedure, using dedicated signalling, systeminformation associated with a cell of the base station, when in said RRCconnected mode; and when the MTC device is in idle mode: obtaining anotification about a system information update in a first periodcomprising a plurality of subframes, using a paging message including asystem information modification indication; and obtaining updated systeminformation in a second period comprising a plurality of subframessubsequent to said first period.
 16. A base station for a communicationsystem in which machine type communication ‘MTC’ devices communicate viasaid base station, the base station comprising: a controller configuredto determine whether to notify said MTC devices that there has been asystem information update; and a transmitter configured to notify anyidle mode MTC devices about the system information update by sending anotification using a paging message, wherein the transmitter is furtherconfigured to initiate a procedure for providing a radio resourcecontrol ‘RRC’ connected mode MTC device with the system informationupdate using dedicated signalling.
 17. A machine type communication‘MTC’ device for a communication system in which MTC devices communicatevia a base station, the MTC device comprising: a controller configuredto establish a radio resource control ‘RRC’ connection with said basestation to enter an RRC connected mode; and a transceiver configured toobtain, as part of a base station initiated procedure, using dedicatedsignalling, system information associated with a cell of the basestation, when in said RRC connected mode.
 18. The base station accordingto claim 1, wherein said system information modification indication isone bit.
 19. The base station according to claim 1, wherein said firstperiod comprises a BCCH modification period and said second periodcomprises the next BCCH modification period.
 20. The MTC deviceaccording to claim 13, wherein said system information modificationindication is one bit.
 21. The MTC device according to claim 13, whereinsaid first period comprises a BCCH modification period and said secondperiod comprises the next BCCH modification period.